Fuel cell stacks operate at relatively high voltage levels and higher temperatures. Liquid flowing through a coolant loop is typically used to control the temperature of the fuel cell stack. The coolant loop typically includes radiators, pumps, tubes and/or other components. To improve safety, steps are typically taken to isolate the high voltage levels of the fuel cell stack from the coolant flowing in the coolant loops. In other words, to provide electrical isolation, the coolant loops should be either electrically isolated or non-conductive coolant should be used.
Current approaches employ very low-conductivity or isolating coolant and long/thin isolating coolant tubes. For example, the low-conductivity coolant can be de-ionized (DI) water or isolating coolant could be oil. The low-conductivity or isolating coolants typically have significant performance disadvantages when compared to higher conductivity coolants, such as automotive (i.e. water and glycol-based) coolants. For example, the isolating coolants typically have low heat capacity, low heat conductivity and high viscosity (e.g. oil). The isolating coolants therefore adversely impact system power density, radiator size, radiator fan size, and/or coolant pump power. The low-conductivity coolants may also pose various environmental constraints. The low-conductivity coolants lack anti-freeze characteristics and/or may cause corrosion (e.g., de-ionized water). Contaminations in the coolant system also tend to increase the conductivity of a low-conductivity coolant over time and hence isolation gets worse.